import java.util.concurrent.Executors;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReadWriteLock;

import java.util.concurrent.locks.ReentrantReadWriteLock;

public class RwlDowngradeDemo{

public static volatile boolean writable = false;

public static void main(String[] args){

ReadWriteLock rwl = new ReentrantReadWriteLock();

ExecutorService es = Executors.newFixedThreadPool(5);

es.submit(new Runnable(){

public void run(){

try{

rwl.writeLock().lock();

if(writable){

System.out.println(Thread.currentThread() + " Writing something, " + "with " + rwl.writeLock());

writable = true;

}else{

// read

rwl.readLock().lock();

System.out.println(Thread.currentThread() + " Reading something, " + "with " + rwl.readLock());

}

}catch(Exception e){

e.printStackTrace();

}finally{

System.out.println(rwl.writeLock() + ", " + rwl.readLock());

rwl.writeLock().unlock();

System.out.println("WriteLock released: \n" + rwl.writeLock() + ", " + rwl.readLock());

rwl.readLock().unlock();

System.out.println("ReadLock released: \n" + rwl.writeLock() + ", " + rwl.readLock());

}

es.shutdown(); // If you want the application end, you need to call the shutdown method otherwise it will be waiting for new runnables.

}

});

}

}